Processes for preparing and utilizing partially de-ashed solid-fuel-water slurries and conveying the slurry by various conveying means, such as pumps, are known. O. Schwartz and H. Merten, Brennstoff Waerme Kraft 18 (10), 474-8 (1966) (Ger) describe a pilot plant in which coal was pulverized dry or wet in ball mills and disk grinders to provide particles up to 77% finer than 0.06 mm (60 .mu.m).
Other processes are described in U.K. Pat. No. 711,105; French Pat. No. 1,581,112; and U.S. Pat. Nos. 3,423,313; 3,682,114; 3,941,552; 3,950,147; and 3,996,026, all of which are discussed in applicant's copending U.S. patent application Ser. No. 790,337, filed Apr. 25, 1977, which portion of said application Ser. No. 790,337 is hereby incorporated by reference herein.
In addition to the above-listed patents, McMurtrie, U.S. Pat. No. 3,019,059, issued Jan. 30, 1962, describes a process for transporting finely divided coal solids by forcing through a conduit an aqueous slurry containing up to 50% solids and containing a minor proportion of coal acids which are added to improve pumpability and to prevent settling during pumping. At the receiving end of the conduit, the slurry is filtered or otherwise processed to remove the water and coal acids and to recover the coal solids for use. Alkali metal and ammonium salts of humic acids are included in the term "coal acids".
Also, Reichl, U.S. Pat. No. 3,073,652, issued Jan. 15, 1963 describes a method of transporting coal over long distances for conversion at distant locations which comprises obtaining coal having a spectrum of sizes and between about 20 and 40 percent by weight of (-)325 mesh particles, (-44 .mu.m), preparing a water slurry comprising between 35 and 60 percent by weight of said coal in water, pumping said slurry through a pipeline at a velocity of between about 3 and 7 feet per second over long distances to a distant location, interrupting the transportation of said slurry at said distant location, thereafter removing a portion of said water from said slurry to provide a concentrated slurry having a solids concentration of between 60 and 75 percent by weight of said coal in said water, pumping said concentrated slurry through a second pipeline over a shorter distance to a second location, and converting the coal in said concentrated slurry at said second location, or burning the concentrated slurry directly, if the burner is suitable for such burning.
Also, Clancey et al., U.S. Pat. No. 3,762,887, issued Oct. 2, 1973, describes a homogeneous composition of matter suitable for use as a liquid fuel consisting essentially of particulate coal and water in the relative proportions of 54 to 69 percent by volume of coal (61.3 to 75.0 wgt %) and 46 to 31 percent by volume of water, said particulate coal having a size distribution substantially as follows: 0 percent by weight on 4 mesh Tyler Standard screen, 18 to 33 percent by weight less than 325 mesh, less than 60 percent by weight between 4 and 28 mesh, and the balance in the size range of 28 to 325 mesh. The coal-water slurry is described as being pumpable, storable and directly burnable in a cyclone burner.
Commercially operated coal-slurry pipelines have been in operation for many years in the United States. Such pipelines and their successes, failures, and problems have been described in various publications, including the following:
"The Black Mesa Story" by F. H. Love, Pipeline Engineer, November 1969;
"Slurry Pipelines, Energy Movers of the Future" by E. J. Wasp, and T. L. Thompson, Oil and Gas Journal, Dec. 24, 1973;
"Research and Development for Slurry Pipeline System Design" by T. C. Aude and R. L. Gandhi, Bechtel, Inc., San Francisco, prepared for delivery at "The Second International Technical Conference on Slurry Transportation", Las Vegas, Nev., Mar. 2-4, 1977;
"Operating Experiences at the 1580 MW Coal Slurry Fired Mohave Generating Station" by M. L. Dina, presented at The International Conference on Slurry Transportation at Battelle Memorial Institute, Columbus, Ohio, Feb. 3, 1976;
"Utilization of Pipeline Delivered Coal", by P. E. Snoek et al., Bechtel, Inc., San Francisco, for ASME Joint Power Generation Conference, Buffalo, N.Y., Sept. 20, 1976; and
"Coal Slurry Pipelines", Van Nostrand Scientific Encyclopedia, fifth edition, 1976, Page 58.
The problem of preparing coal-water slurry for long distance delivery through pipelines ranging in diameter from about 4" to 48" to be burned at the delivery depot is to be distinguished from the problem of preparing a coal-water slurry from which a more concentrated slurry or a coal "cake" is prepared at a use site and burning the concentrated coal-water slurry or "cake" so prepared. Also, the problem of burning coal-water slurry in a turbulent burner is to be distinguished from burning coal-water slurry in a cyclone burner of a furnace. For examples of burners, see Chemical Technology: An Encyclopedic Treatment, J. F. Van Oss, Barnes and Noble Books, Div. Harper & Row, Publ., Inc. N.Y. 1971 Vol. II, Pages 722-725.